Regression since 0.57.0: Inference chain gets broken in certain situations

[villesau]

Repro steps can be found from this comment: flow-typed/flow-typed#1731 (comment)

So in a nutshell, Flow can't infer the type from passed in object property which is assigned to object passed out. This causes unsoundness: you expect type to be what it is not. This seems pretty bad regression to me.

You can see in the test case that the component expects number, but string is passed in. If you test the libs on versions earlier than 0.57.0, Flow is able to infer the type and fails the test appropriately.

To see the issue clearly, you can remove the rest of the tests but the one comment is pointing to. Also others that top most connect definition are not relevant to point out this bug.

[villesau]

Here is a slightly better scoped example of the issue: try flow

See that the type fromStateToProps is number in type State, but Props expects it to be string. If you change flow version to 0.56.0, Flow detects the wrong type, but newer versions don't

[SamChou19815]

We no longer support this kind of inference.